Cutting knife



United States Patent 697. 654. 686. 679: 30/169. 357. 241(Cursory): '1 44/212,24 1; 29/95 [56] References Cited UNITED STATES PATENTS 378,741 2/1888 Trout 144/212 1,273,249 7/1918 Lurker 29/95 Primary ExaminerAndrew R. Juhasz Assistant Examiner Leon Gilden Attorney-Rowland V. Patrick ABSTRACT: Cutting knife with first and second sides, the second side having a flat surface and a beveled surface meeting the first side to form a cutting edge. The first side has an elongated surface and a portion at the edge region tapering outwardly toward the cutting edge so that it extends away from the second side beyond the first sides elongated surface.

22 20 Z 4 1 T i 0 Patented Oct. 6, 1970 CUTTING KNIFE This invention relates to cutting knives for sheet materials and more particularly for reams of paper.

For cutting reams of paper long heavy knives (as much as over 125 inches in length) having a leading cutting edge are used. The contour of the cross section of such a knife is selected so that as the cutting edge goes through reams of paper the friction of the cut paper edges on the sides of the knife above the cutting edge is minimized as much as possible. The thickness of the knife is usually diminished above the cutting edge to provide clearance to lessen friction. Quick clearance is desirable to eliminate friction. unevenness of sheets and paper dust. The knife is bolted to a driving head in operation so that an additional requirement of the contour of the cross section is that it be adapted for connection to a variety of heads easily and securely.

it is an object of this invention to provide an improved cutting knife for sheet materials that minimizes friction between the knife and the materials during the cutting operation, and that retains its desirable characteristics after repeated sharpenings, and therefore during the entire life of the knife.

The invention features a cutting knife having a first side and a second beveled side, the second beveled side having a fiat surface and a beveled surface meeting the first side to form a cutting edge. The first side has an elongated surface and a taper portion at the cutting edge region tapering away from the second side toward the cutting edge so that the cutting edge extends away from the plane of the second sides flat surface beyond the plane of the first sides elongated surface to give clearance. in preferred embodiments the taper portion lies in a single plane, and is at an angle of the order of 10 to 025. optimally 015. to the elongated surface of the first side. If the surface of the first side is fiat, the second side surface may be parallel to it.

Other objects, features and advantages will appear from the following description of a preferred embodiment of the invention, together with the attached drawing thereof, which is a cross-sectional view of a cutting knife embodying the inventron.

The knife shown is five inches wide. It has a first side, generally designated 10, and a second beveled side, generally designated 12. The second side 12 has a flat (that is, lying in one plane) surface 14 and the first side 10 has, in the embodiment shown, a flat surface 16 which is parallel to surface 14. Second side 12 also includes a beveled surface 18 at a conventional angle of about 22 to flat surface 14 meeting first side 10 to form a cutting edge 20.

First side 10 includes a taper portion 22. Taper portion 22 is shown as being flat (lying in one plane) and tapers away from second side 12 toward cutting edge 20. For the five inch wide knife shown, taper portion 22 extends one and three fourths inches back from cutting edge 20. In this instance, the taper angle a which the taper portion 22 makes with flat surface 16 of first side 10 is 015. Over the distance of one and three fourths inches the taper angle causes taper portion 22 to rise about .007 inch. An additional step 24 of taper portion 22 above first side flat surface 16 of about .003 inch may be present and cause cutting edge 20 to lie about .010 inch beyond the plane of flat surface 16 offirst side 10. In the cutting knife shown the distance d, between the parallel flat surfaces 14 and 16 of the second and first sides is .485 inch so that the distance d between shear edge 20 and the extension of flat surface 14 ofthe second side is .495 inch.

In the cutting operation, cutting edge 20 cuts and the sheets of paper are separated by about .495 inch by the beveled surface 18 of the second side. The protrusion of cutting edge 20 away from second side 12 beyond the plane of the first sides flat surface 16 by about .010 inch provides for clearance between the sheets of paper and surface 16, minimizing friction, paper movement and dust accumulation as cutting edge 20 continues to pass through the ream of paper which often is 4 to 5 inches in height. During the life of the knife it may be ground back in repeated sharpenings, so that its full width is reduced by as much as 1 and /2 inch. Because the clearance provided after 1 /2 inch has been ground away is more than sufficient to prevent rubbing, the cutting operation remains satisfactory throughout the life of the knife, there always being more than that amount of clearance until the knife is ground away to over 1 A inch reduction in width.

While the surfaces 14 and 16 are both shown to be flat and parallel, it is contemplated that surface 16 may have some concavity or taper so that the thickness of the knife at step 24 is greater than the knife thickness at the end d, or surface 16 even may merge into surface 22. Surface 22 likewise may have some concavity due to the method of manufacture though a flat surface is preferred.

Finally, as is obvious, angle a may be greater so that surface 22 merges into surface 16 when surface 16 is parallel to surface 14.

Other embodiments will occur to those skilled in the art and are within the following claims.

I claim:

1. An elongated cutting knife for cutting multiple layers of sheet material, said knife having:

a first side;

a second beveled side, both extending in the general direction of the cutting motion of the knife; said second beveled side including a fiat surface and a beveled surface meeting said first side at an angle of about 22 to form a cutting edge; and

said first side including a flat surface and a taper portion tapering away from said second side at an angle of about 015 to said first side flat surface toward said cutting edge so that said cutting edge extends away from the plane of said second side flat surface beyond the plane of said first side flat surface to give clearance, whereby when said knife is ground back from said cutting edge during repeated sharpenings resulting in a removal of a substantial section of said taper portion it will maintain ample clearance due to said taper portion throughout the useful life of the knife. 

